Route search device, route search method, and route search program

ABSTRACT

Routes can be found while improving the convenience of guidance for users. A route-searching device includes a search-condition acquisition unit that acquires search conditions for searching a route including a starting point and a destination; a route-data storage unit that stores a link ID, the node IDs of the starting point and the end point of a link, and road network information concerning a road network and including a link length; an instruction-data storage unit that stores instruction data including a type associated with the node ID, a value for the type, and a coefficient for the value; and a route generation unit that generates route candidates including the shortest route based on the search conditions and the road network information, calculating, for each of the route candidates, an index value based on information included in the instruction data, and outputting, as a search route, the route candidate with the index value improved from the index value of the shortest route.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application filed under 35U.S.C. § 371 claiming priority to International Patent Application No.PCT/JP2019/019189, filed on 14 May 2019, the disclosure of which ishereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosed technique relates to a route-searching device, aroute-searching method, and a route-searching program.

BACKGROUND ART

As conventional art, a technique is provided to search a route for auser to a destination and guide the user according to the search routein a map application or pedestrian navigation on a smartphone or thelike and car navigation. As an example of a route-searching technique, atechnique of searching a route from a starting point to a destinationbased on a shortest-route search algorithm, for example, Dijkstra'salgorithm is available as described in NPL 1. Moreover, a method calledturn-by-turn navigation for providing guidance, for example, “Turn rightin 30 m” for right and left turns is available (for example, NPL 2).

In the generation of an instruction in turn-by-turn navigation, theinstruction may include information on symbols and the shapes ofintersections such as an end of a street. Symbols are, for example,information called POI (Point of Interest) including a convenience storeand a post office at an intersection where a right or left turn is to bemade. Since such information is included, an instruction like “Turn leftat the corner of the post office” or an instruction like “Turn right atthe end of the street” are generated to encourage a user to recognize anintersection where a turn is to be made. This technique is widely used(for example, NPL 3).

CITATION LIST Non Patent Literature

-   [NPL 1] E. W. Dijkstra “A Note on Two Problems in Connexion with    Graphs”, Numerische Mathematik, vol. 1, 1959, pp. 269-271,    doi:10.1007/BF01386390.-   [NPL 2] Kacorri, Hernisa, et al. “Environmental Factors in Indoor    Navigation Based on Real-World Trajectories of Blind Users”.    Proceedings of the 2018 CHI Conference on Human Factors in Computing    System s. ACM, 2018.-   [NPL 3] Furukawa H., Nakamura Y. (2013) A Pedestrian Navigation    Method for User's Safe and Easy Wayfinding. In: Kurosu M. (eds) Huma    n-Computer Interaction. Users and Contexts of Use. HCl 2013. Lecture    Notes in Computer Science, vol 8006. Springer, Berlin, Heidelberg.-   [NPL 4] Yen, Jin Y. “Finding the k shortest loopless paths in a    network”. management Science 17.11 (1971): 712-716.

SUMMARY OF THE INVENTION Technical Problem

However, when instructions are generated as described in NPL 2 and NPL 3by using the shortest-route search algorithm described in NPL 1, POIserving as symbols may be excluded from a shortest route. Thus,unfortunately, POI may be excluded from an instruction of routeguidance.

The disclosed technique has been devised in view of the problem. Anobject of the disclosed technique is to provide a route-searchingdevice, a route-searching method, and a route-searching program thatenable route searching while improving the convenience of guidance forusers.

Means for Solving the Problem

A first aspect of the present disclosure is a route-searching deviceincluding: a search-condition acquisition unit that acquires searchconditions for searching a route including a starting point and adestination; a route-data storage unit that stores a link ID, the nodeIDs of the starting point and the end point of a link, and road networkinformation concerning a road network and including a link length; aninstruction-data storage unit that stores instruction data including atype associated with the node ID, a value for the type, and acoefficient for the value; and a route generation unit that generatesroute candidates including the shortest route based on the searchconditions and the road network information, calculates, for each of theroute candidates, an index value based on information included in theinstruction data, and outputs, as a search route, the route candidatewith the index value improved from the index value of the shortestroute.

A second aspect of the present disclosure is a route-searching method inwhich a computer performs the steps of: acquiring search conditions forsearching a route including a starting point and a destination;generating route candidates including a shortest route based on thesearch conditions, a stored link ID, the node IDs of a starting pointand an end point of a link, and road network information concerning aroad network and including a link length; calculating, for each of theroute candidates, an index value based on information included ininstruction data including a type associated with the node ID, a valuefor the type, and a coefficient for the value; and outputting, as asearch route, the route candidate with the index value improved from theindex value of the shortest route.

A third aspect of the present disclosure is a route-searching programcausing a computer to acquire search conditions for searching a routeincluding a starting point and a destination, generate route candidatesincluding a shortest route based on the search conditions, a stored linkID, the node IDs of a starting point and an end point of a link, androad network information concerning a road network and including a linklength, calculate, for each of the route candidates, an index valuebased on information included in instruction data including a typeassociated with the node ID, a value for the type, and a coefficient forthe value, and output, as a search route, the route candidate with theindex value improved from the index value of the shortest route.

Effects of the Invention

According to the disclosed technique, routes can be found whileimproving the convenience of guidance for users.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating the configuration of aroute-searching system according to the present embodiment.

FIG. 2 is a block diagram illustrating the hardware configuration of aroute-searching device.

FIG. 3 is an image of a database table of a route-data storage unitaccording to the present embodiment.

FIG. 4 is an image of a database table of an instruction-data storageunit according to the present embodiment.

FIG. 5 is a flowchart indicating the flow of route searching by theroute-searching device.

FIG. 6 is a flowchart indicating the detail of route generation.

FIG. 7 illustrates an image of a comparison between a conventionaltechnique and the technique of the present embodiment regarding therelationship between symbols on a search route.

DESCRIPTION OF EMBODIMENTS

An example of an embodiment of the disclosed technique will be describedbelow with reference to the accompanying drawings. In the drawings, thesame or equivalent constituent elements and parts are indicated by thesame reference numerals. Dimensional ratios in the drawings areexaggerated for purposes of illustration and may be different fromactual ratios.

The configuration of the present embodiment will be described below.

FIG. 1 is a block diagram illustrating the configuration of aroute-searching system according to the present embodiment.

As illustrated in FIG. 1 , a route-searching system 1 includes aroute-searching device 10 and a navigation device 40. Theroute-searching device 10 includes a search-condition acquisition unit110, a route generation unit 120, an output unit 130, a route-datastorage unit 200, and an instruction-data storage unit 300. Thenavigation device 40 includes an instruction generation unit 400 and adisplay unit 410.

FIG. 2 is a block diagram illustrating the hardware configuration of theroute-searching device 10.

As illustrated in FIG. 2 , the route-searching device 10 includes a CPU(Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (RandomAccess Memory 13, a storage 14, an input unit 15, a display unit 16, anda communication interface (I/F) 17. The configurations are connected viaa bus 19 so as to communicate with one another.

The CPU 11 is a central processing unit that executes various programsand controls the units. Specifically, the CPU 11 reads a program fromthe ROM 12 or the storage 14 and executes the program with the RAM 13serving as a work area. The CPU 11 controls the configurations andperforms various computations according to programs stored in the ROM 12or the storage 14. In the present embodiment, a route-searching programis stored in the ROM 12 or the storage 14.

The ROM 12 stores a variety of programs and data. The RAM 13 as a workarea temporarily stores programs or data. The storage 14 includes an HDD(Hard Disk Drive) or an SSD (Solid State Drive) and stores variousprograms including an operating system and a variety of data.

The input unit 15 includes pointing devices such as a mouse and akeyboard and is used for performing various inputs.

The display unit 16 is, for example, a liquid crystal display thatdisplays a variety of information. The display unit 16 may be a touchpanel acting as the input unit 15.

The communication interface 17 is an interface for communications withother devices, e.g., a terminal. For example, standards such as Ethernet(registered trademark), FDDI, and Wi-Fi (registered trademark) are used.

The navigation device 40 may have the same hardware configuration as theroute-searching device 10 and thus the detailed explanation thereof isomitted.

The functional configurations of the route-searching device 10 will bedescribed below. The route-searching program stored in the ROM 12 or thestorage 14 is read by the CPU 11 and is developed and executed in theRAM 13, so that the functional configurations are implemented.

FIG. 3 is an image of a database table of the route-data storage unit200 according to the present embodiment. In the table of the route-datastorage unit 200, a junction of a road, e.g., an intersection serves asa node, and a road divided by a road network serves as a link. Thedatabase of the route-data storage unit 200 is a reference database ofan initial node ID serving as the node of the starting point of theroad, a terminal node ID serving as the node of the endpoint, and a link(road) length d. A link ID serving as a road ID is used as a key.Information on a road network, including the link length d, will bereferred to as road network information. Hereinafter, a variety ofinformation included in the road network information is assumed to bestored in the route-data storage unit 200.

FIG. 4 is an image of a database table of the instruction-data storageunit 300 according to the present embodiment. The database of theinstruction-data storage unit 300 includes, as instruction data with anode ID serving as a key, types including POI and the shapes ofintersections, values including convenience stores and T-junctions, anda coefficient a (hereinafter, a is omitted unless the indication isnecessary) that contributes to the generation of instructions during asearch for a route. The database of the instruction-data storage unit300 is configured to refer to information included in the instructiondata. The value is an object indicating the specific symbol orcharacteristic of the type. The coefficient is, for example, acoefficient indicating the degree of contribution of the value toguidance. The type, the value, and the coefficient may be freelydesigned according to the scene of usage of navigation and the purposeof an application. For example, in order to include a landmark, e.g., atourist attraction as a POI, “type: POI, value: xxx temple, coefficient:0.4” is added. Moreover, in order to examine whether an intersection islikely to be conjected or not in the route generation unit 120, “type:congestion degree, value: large, coefficient: 1.5” may be added. Thevalue indicates the name and characteristic of a landmark for the sakeof explanation. The value is actually an identifiable value.Hereinafter, it is assumed that the type, the value, and the coefficientare stored in the instruction-data storage unit 300.

The route-searching device 10 acquires, as an input, search conditionsfor searching a route including a starting point and a destination.

The route generation unit 120 generates route candidates including ashortest route based on the search conditions and the road networkinformation. The route generation unit 120 calculates index values forthe route candidates based on information included in the instructiondata and outputs, as an output route, the route candidate with an indexvalue improved from that of the shortest route. Specifically, the k-thshortest path algorithm described in NPL 4 is used to generate routecandidates in the ascending order of route lengths. Moreover, for theroute candidates having route lengths equal to or less than a routelength determined with a predetermined magnification relative to theshortest route, a corrected index value is calculated based on theinformation included in the instruction data so as to reduce or increasea route length obtained as the sum of the lengths of links included inthe route candidates.

The detail of the processing of the navigation device 40 will bedescribed after the explanation of the operations of the route-searchingdevice 10.

The operations of the route-searching device 10 will be described below.

FIG. 5 is a flowchart indicating the flow of route searching by theroute-searching device 10. The CPU 11 reads the route-searching programfrom the ROM 12 or the storage 14 and develops and executes the programin the RAM 13, so that a route is found. The route-searching device 10receives the search conditions as an input and performs the followingprocessing:

In step S200, as acquisition of the search conditions, the CPU 11acquires the search conditions including a starting point and adestination in the search-condition acquisition unit 110 and outputs thesearch conditions to the route generation unit 120. The searchconditions indicate a guidance route from a user or an external system.

In step S210, as route generation in the route generation unit 120, theCPU 11 then acquires the road network information from the route-datastorage unit 200 and information included in the instruction data fromthe instruction-data storage unit 300. The CPU 11 generates a searchroute s*, which is a route found based on the acquired information, andoutputs the route to the output unit 130.

In step S220, as the output processing of the search route in the outputunit 130, the CPU 11 outputs the search route s* to the navigationdevice 40.

FIG. 6 is a flowchart indicating the detail of route generation.According to the flowchart of FIG. 6 , the route generation of the routegeneration unit 120 according to the present embodiment will bedescribed below. The following processing is performed by the CPU 11serving as the route generation unit 120.

In step S300, the CPU 11 receives the search conditions including astarting point and a destination from the search-condition acquisitionunit 110.

In step S311, the CPU 11 acquires the road network information from theroute-data storage unit 200 by using the search conditions that includethe starting point and the destination and are acquired in step S300.The road network information to be acquired includes a link ID, aninitial node ID and a terminal node ID that are associated with the linkID, and a link length.

In step S312, the CPU 11 then generates top-K route candidates in theascending order of distances between a starting point and a destinationby using the K-th shortest path algorithm, for example, the Yen'salgorithm (NPL 4). A set of route candidates is denoted as R, and thek-th shortest route candidate is denoted as r_(k). The shortest route isdenoted as r₁. In the route candidate set R, the first route r₁ havingthe shortest distance serves as a temporary solution s* (s*=r₁) of asearch route to be outputted. If K is set at a small value, e.g., 5 or10, a computation time is determined as a practical value even by anunderperforming computer. If K is set at a large value, e.g., 100 or1000, satisfactory results can be found over a wider range.

In step S320, the CPU 11 sets the values of k (k=1, . . . , K). In thiscase, the CPU 11 may sequentially set the values of k from 2 except for1, the shortest route candidate. Until the completion of a loop, thatis, until k=K is satisfied, the CPU 11 repeats the following processing:

In step S321, for each route of the route candidate set R, the CPU 11first determines whether a distance dist(r_(k)) of the route r_(k) is atmost w times longer than the shortest route r₁ according to a comparisonexpressed by Formula (1):

$\begin{matrix}{{{dist}\left( r_{k} \right)} \leq {{{dist}\left( {r1} \right)}*w}} & (1)\end{matrix}$

If the conditions of Formula (1) are satisfied, the CPU 11 advances tostep S322. Otherwise the CPU 11 advances to step S330.

Thus, even if the index values of route candidates are preferable in thesubsequent processing, the output of a search route with quite a longtravel distance as compared with the shortest route r₁ can be avoided.Moreover, by using the route candidates r_(k) sequentially sorted inorder of distance in the route candidate set R, an unnecessary search iscancelled so as to enhance the speed of processing. The value of w canbe determined according to an application. In the case of incorporationinto a pedestrian navigation application, for example, 1.5 is setaccording to 1≤w≤2.

In step S322, the CPU 11 acquires information (a type, a value, and acoefficient) included in instruction data on the route r_(k), from theinstruction-data storage unit 300.

The information included in the instruction data is defined as follows:The set of node IDs for nodes included in the route candidates r_(k) isdenoted as V_(k), the set of link IDs is denoted as E_(k), each node IDis denoted as v∈V_(k), and each link ID is denoted as e∈E_(k). Aninitial node is denoted as i, the set of initial nodes for a link e_(i)included in the set E_(k) of link IDs is denoted as I_(k), a coefficientfor an initial node included in the link e_(i) is denoted as a_(i), andthe length of the link e_(i) for the set E_(k) of link IDs is denoted asd_(i). Thus, in step S322, the CPU 11 may acquire a type, a value, andthe coefficient a_(i) for the set I_(k) of initial nodes.

In step S323, the CPU 11 calculates an index value score(r_(k)) of theroute candidates r_(k) based on acquired information (a type, a value,and a coefficient) on POIs or the like. The sum of coefficients for allthe types of v of node IDs is denoted as a_(v). If the node ID of theinstruction-data storage unit 300 in FIG. 4 is v=1000, POI: thecoefficient a of a convenience store=0.1 and the shape of anintersection: the coefficient a of a T-junction=0.3 are determined.Thus, a_(v) is obtained as a₁₀₀₀=0.1+0.3=0.4. If the index valuescore(r_(k)) is defined as a value determined by, for example,subtracting the sum a_(v) of coefficients of types included in v of nodeIDs from the length d of each link, Formula (2) can be used as expressedbelow. In Formula (2), max( ) is a function for acquiring a maximumvalue, and θ is a threshold value for a subtraction of a link length.For example, 0.5 is used as a value of 0<θ<1.

$\begin{matrix}{{{score}\left( r_{k} \right)} = {{\sum}_{i}d_{i}^{\star}{\max\left( {\left( {1\  - a_{i}} \right),\theta} \right)}}} & (2)\end{matrix}$

In step S324, the CPU 11 compares the index value score(r_(k))calculated by Formula (2) and an index value score(s*) for the temporarysolution s* according to Formula (3) below. In Formula (2), the indexvalue for reducing a route length is used. In the case of an index valuefor increasing a route length, for example, a_(i) may be added.

$\begin{matrix}{{{score}\left( r_{k} \right)} < {{score}\left( s^{\star} \right)}} & (3)\end{matrix}$

If the conditions of Formula (3) are satisfied, the CPU 11 advances tostep S325. Otherwise the CPU 11 repeats the processing with subsequentset k in step S320 through the repeated loop until k=K is obtained.

In step S325, the CPU 11 determines that the index value has improvedand updates the temporary solution s* by r_(k). After the update, theCPU 11 repeats the processing with subsequent set k in step S320 throughthe repeated loop until k=K is obtained. As described above, the CPU 11repeats the processing until the CPU 11 exits the loop in step S321 orobtains k=K.

In step S330, the CPU 11 outputs, to the output unit 130, s* as a searchroute that is obtained as a search result and completes the processing.The search route s* includes at least a link ID and a node ID that arenecessary for generating a route.

The guidance of the navigation device 40 according to the presentembodiment will be described below. The instruction generation unit 400acquires the search route s* that is outputted from the output unit 130.Furthermore, the instruction generation unit 400 acquires information onthe value of the corresponding node ID from the node ID included in thesearch route s* with reference to the instruction-data storage unit 300,and generates guidance information. A specific example will be describedbelow. For example, it is assumed that the node ID included in thesearch route s* indicates a node around an intersection and aconvenience store is located near the node. The instruction generationunit 400 acquires a type “POI” and a value “convenience store” with thenode ID serving as a key and generates information on the acquired typeand value as guidance information.

FIG. 7 illustrates an image of a comparison between a conventionaltechnique and the technique of the present embodiment regarding therelationship between symbols on a search route. In the example of FIG. 7, the use of an ordinary route-search algorithm according to theconventional technical displays a search route that is the shortest butturns at an intersection not including any POIs as indicated by abroken-line part in the example of the search route. The technique ofthe present embodiment can display a search route that includes a POInecessary for an instruction as indicated by a solid-line part.

As guidance information of the conventional technique, for example, aninstruction “Turn right at the corner of the convenience store” isgenerated. In the route searching of the present embodiment, aninstruction “turn right at the first intersection” is generated for aninstruction in typical turn-by-turn navigation according to theconventional method. However, in the present embodiment, an instruction“Turn right between a tempura restaurant and a convenience store at thefirst intersection” can be generated. The instruction generation unit400 displays the generated guidance information by means of the displayunit 410. In the example of FIG. 7 , instructions are displayedaccording to the technique of the present embodiment as follows: “1.Turn right between the tempura restaurant and the convenience store atthe first corner. 2. Go ahead to the school at the end of the street andturn left. 3. Go straight ahead to the destination”. To enable suchguidance, for the node ID of a node for the link of a road where a rightturn is made in the guidance of 1., “tempura restaurant” and“convenience store” are associated with the values of theinstruction-data storage unit 300 and are set with effectivecoefficients. Thus, by referring to a value set at a coefficient valuenot smaller than a threshold value during the acquisition of theinstruction generation unit 400 or adding information on values havingeffective coefficients to found information s* in advance, properguidance information can be generated. As described above, the techniqueof the present embodiment enables guidance including landmarks servingas symbols for a user. Such guidance cannot be achieved only byoutputting a shortest route.

As has been mentioned, the route-searching system of the presentembodiment can search a route while providing convenient guidance for auser. Moreover, guidance information on search routes can be displayedwhile offering enhanced convenience to a user.

Routes found by reading software (program) according to the embodimentmay be found by various processors other than a CPU. In this case, theprocessors may be, for example, a PLD (Programmable Logic Device) havinga circuit configuration that is changeable after the manufacturing of anFPGA (Field-Programmable Gate Array) or the like and a dedicatedelectric circuit acting as a processor with a circuit configurationdesigned specifically for performing specific processing for an ASIC(Application Specific Integrated Circuit). Alternatively, a route may befound by one of the processors or a combination of at least twoprocessors of the same type or different types (for example, multipleFPGAs and a combination of a CPU and an FPGA). More specifically, thehardware structure of the processors is an electric circuit in whichcircuit elements such as semiconductor devices are combined.

In the foregoing embodiment, the route-searching program is stored(installed) in advance in the storage 14. The present invention is notlimited to this configuration. The program to be provided may be storedin non-transitory storage media such as a CD-ROM (Compact Disk Read OnlyMemory), a DVD-ROM (Digital Versatile Disk Read Only Memory), and USB(Universal Serial Bus) memory. Alternatively, the program may bedownloaded from an external device via a network.

Regarding the foregoing embodiment, appendixes are disclosed as follows:

APPENDIX 1

A route-searching device comprising: a memory; and at least oneprocessor connected to the memory, wherein the processor is configuredto acquire search conditions for searching a route including a startingpoint and a destination, generate route candidates including theshortest route based on the search conditions, a stored link ID, thenode IDs of the starting point and end point of a link, and road networkinformation concerning a road network and including a link length,calculate, for each of the route candidates, an index value based oninformation included in instruction data including a type associatedwith the node ID, a value for the type, and a coefficient for the value,and output, as a search route, the route candidate with the index valueimproved from the index value of the shortest route.

APPENDIX 2

A non-transitory storage medium in which a route-searching program isstored, the route-searching program causing a computer to acquire searchconditions for searching a route including a starting point and adestination, generate route candidates including the shortest routebased on the search conditions, a stored link ID, the node IDs of thestarting point and end point of a link, and road network informationconcerning a road network and including a link length, calculate, foreach of the route candidates, an index value based on informationincluded in instruction data including a type associated with the nodeID, a value for the type, and a coefficient for the value, and output,as a search route, the route candidate with the index value improvedfrom the index value of the shortest route.

REFERENCE SIGNS LIST

-   -   1 Route-searching system    -   10 Route-searching device    -   40 Navigation device    -   110 Search-condition acquisition unit    -   120 Route generation unit    -   130 Output unit    -   200 Route-data storage unit    -   300 Instruction-data storage unit    -   312 Step    -   324 Step    -   330 Step    -   400 Instruction generation unit    -   410 Display unit

The invention claimed is:
 1. A route-searching device comprising: asearch-condition acquirer configured to acquire search conditions forsearching a route including a starting point and a destination; aroute-data store configured to store a link ID, node IDs of a startingpoint and an end point of a link, and road network informationconcerning a road network and including a link length; aninstruction-data store configured to store instruction data including atype associated with the node ID, a value for the type, and acoefficient for the value; and a route generator configured to: generateroute candidates including a shortest route based on the searchconditions and the road network information, determine, for each of theroute candidates, an index value based on information included in theinstruction data, wherein, for the route candidates having route lengthsequal to or less than a route length determined with a predeterminedmagnification relative to the shortest route, the route generatorupdates the index value based on the information included in theinstruction data so as to reduce or increase a route length obtained asa sum of lengths of links included in the route candidates having routelengths equal to or less than the route length determined with thepredetermined magnification, and output, as a search route, the routecandidate with the index value improved from the index value of theshortest route.
 2. The route-searching device according to claim 1,wherein the route generator generates the route candidates in anascending order of route lengths by using a predetermined algorithm. 3.The route-searching device according to claim 2, wherein the index valueis generated by correcting the lengths of the links included in theroute candidates having a route length equal to or less than the routelength determined with the predetermined magnification, according to acoefficient corresponding to the type associated with the node IDincluded in the link.
 4. The route-searching device according to claim1, wherein if the value is included in the search route, information onthe value corresponding to the search route is included.
 5. Acomputer-implemented method for route searching, comprising: acquiring,by a search-condition acquirer, search conditions for searching a routeincluding a starting point and a destination; generating, by a routegenerator, route candidates including a shortest route based on thesearch conditions, a stored link ID, node IDs of a starting point and anend point of a link, and road network information concerning a roadnetwork and including a link length; determining, by the routegenerator, for each of the route candidates, an index value based oninformation included in instruction data including a type associatedwith the node ID, a value for the type, and a coefficient for the value,wherein for the route candidates having route lengths equal to or lessthan a route length determined with a predetermined magnificationrelative to the shortest route, the route generator updates the indexvalue based on the information included in the instruction data so as toreduce or increase a route length obtained as a sum of lengths of linksincluded in the route candidates having route lengths equal to or lessthan the route length determined with the predetermined magnification;and providing, as a search route, the route candidate with the indexvalue improved from the index value of the shortest route.
 6. Acomputer-readable non-transitory recording medium storingcomputer-executable route-searching program instructions that whenexecuted by a processor cause a computer system to: acquire, by asearch-condition acquirer, search conditions for searching a routeincluding a starting point and a destination; generate, by a routegenerator, route candidates including a shortest route based on thesearch conditions, a stored link ID, node IDs of a starting point and anend point of a link, and road network information concerning a roadnetwork and including a link length; determine, by the route generator,for each of the route candidates, an index value based on informationincluded in instruction data including a type associated with the nodeID, a value for the type, and a coefficient for the value, wherein, forthe route candidates having route lengths equal to or less than a routelength determined with a predetermined magnification relative to theshortest route, the route generator updates the index value based on theinformation included in the instruction data so as to reduce or increasea route length obtained as a sum of lengths of links included in theroute candidates having route lengths equal to or less than the routelength determined with the predetermined magnification; and provide, asa search route, the route candidate with the index value improved fromthe index value of the shortest route.
 7. The route-searching deviceaccording to claim 2, wherein if the value is included in the searchroute, information on the value corresponding to the search route isincluded.
 8. The route-searching device according to claim 3, wherein ifthe value is included in the search route, information on the valuecorresponding to the search route is included.
 9. Thecomputer-implemented method according to claim 5, wherein the routegenerator generates the route candidates in an ascending order of routelengths by using a predetermined algorithm.
 10. The computer-implementedmethod according to claim 5, wherein if the value is included in thesearch route, information on the value corresponding to the search routeis included.
 11. The computer-readable non-transitory recording mediumaccording to claim 6, wherein the route generator generates the routecandidates in an ascending order of route lengths by using apredetermined algorithm.
 12. The computer-readable non-transitoryrecording medium according to claim 6, wherein if the value is includedin the search route, information on the value corresponding to thesearch route is included.
 13. The computer-implemented method accordingto claim 9, wherein the index value is generated by correcting thelengths of the links included in the route candidates having a routelength equal to or less than the route length determined with thepredetermined magnification, according to a coefficient corresponding tothe type associated with the node ID included in the link.
 14. Thecomputer-implemented method according to claim 9, wherein if the valueis included in the search route, information on the value correspondingto the search route is included.
 15. The computer-readablenon-transitory recording medium according to claim 11, wherein the indexvalue is generated by correcting the lengths of the links included inthe route candidates having a route length equal to or less than theroute length determined with the predetermined magnification, accordingto a coefficient corresponding to the type associated with the node IDincluded in the link.
 16. The computer-readable non-transitory recordingmedium according to claim 11, wherein if the value is included in thesearch route, information on the value corresponding to the search routeis included.
 17. The computer-implemented method according to claim 13,wherein if the value is included in the search route, information on thevalue corresponding to the search route is included.
 18. Thecomputer-readable non-transitory recording medium according to claim 15,wherein if the value is included in the search route, information on thevalue corresponding to the search route is included.